1. Field of the Invention
The present invention relates to a transmission apparatus, a reception apparatus, a transmission method, and a reception method, and in particular, to a transmission apparatus, a reception apparatus, a transmission method and a reception method, each for efficiently transmitting error information during transmission of digital data such as a video signal, an audio signal, file data or the like.
2. Description of the Related Art
FIG. 8 is a block diagram of a constitution of a digital data transmission system according to the prior art. Referring to FIG. 8, a compression-recording type VTR 101 records a data signal such as a video signal and an audio signal including an error correction code, on a magnetic tape during recording, while the VTR 101 reproduces a reproduced signal from the data signal such as the video signal and the audio signal including the error correction code from the magnetic tape during reproduction. Then, the VTR 101 executes error correction for the reproduced signal, and then, outputs the error-corrected reproduced signal to a transmission apparatus 102. Thereafter, the transmission apparatus 102 converts the inputted reproduced signal into a transmission data signal based on the standard for a digital data transmission line 103 in conformity with the standard for SDTI (Serial Data Transport Interface: the interface for transmitting a compressed digital video signal) specified by SMPTE (Society of Motion Picture and Television Engineers) 305M, for example, and then, the transmission apparatus 102 transmits the transmission data signal to a reception apparatus 104 through the digital data transmission line 103.
On the other hand, the reception apparatus 104 receives the transmission data signal through the digital data transmission line 103, the reception apparatus 104 decodes the received transmission data signal into the video signal in conformity with the standard for a CRT display monitor apparatus 105 and the audio signal, and the reception apparatus 104 outputs the decoded video signal to the CRT display monitor apparatus 105, and this leads to that an image of the video signal is displayed on the CRT display monitor apparatus 105. Also, the reception apparatus 104 outputs the audio signal to a speaker (not shown), which converts the audio signal into a sound of the audio signal and then outputs the sound.
However, when an uncorrectable error occurs during reproduction by the VTR 101, the VTR 101 cannot inform the reception apparatus 104 of the occurrence of the error. Therefore, the reception apparatus 104 performs normal typical decoding regardless of presence or absence of the error, and this causes noise on the CRT display monitor apparatus 105.
Moreover, in order to transmit an error information signal generated by the VTR 101, it is necessary to add at least one-bit error information signal to each word of the video signal. However, the digital data transmission line 103 in conformity with the standard for the above-mentioned SDTI (Serial Data Transport Interface), for example, cannot transmit the above-mentioned error information signal, because a band for transmitting any information signal other than the video signal cannot be sufficiently ensured due to a limitation of the standard for the digital data transmission line 103. Moreover, the error correction code is added to the data signal in order to correct the error in the digital data transmission line 103. Signal processing based on a unit of word or byte is convenient for this addition, and thus the error information signal is not transmitted.
It is an object of the present invention to provide a transmission apparatus, a reception apparatus, a transmission method and a reception method, which do not produce noise when a video signal is reproduced at the receiving side and which can efficiently transmit an error information signal from the transmission apparatus to the reception apparatus.
According to the first aspect of the present invention, there is provided a transmission apparatus comprising:
information generating means for generating error location information at which an error occurs in each block, in accordance with a data signal including a video signal composed of a predetermined first number of words and generated for each block, and an error information signal indicating presence or absence of the error corresponding to the data signal; and
transmitting means for multiplexing the error location information generated by the information generating means and the data signal into a multiplexed signal, and transmitting the multiplexed signal through a transmission line.
The above-mentioned transmission apparatus preferably further comprises converting means for converting a data signal including a video signal composed of a predetermined second number of words and generated for each block, into a data signal including a video signal composed of the first number of words and generated for each block, and outputting the converted data signal to the information generating means and the transmitting means.
Also, according to the second aspect of the present invention, there is provided a reception apparatus comprising:
receiving means for receiving a transmission data signal including a data signal and an error pointer signal through a transmission line, the data signal including a video signal composed of a predetermined first number of words and generated for each block, the error pointer signal indicating error location information at which an error occurs corresponding to the data signal;
demultiplexing means for demultiplexing the transmission data signal received by the receiving means into the data signal and the error pointer signal, and outputting the data signal and the error pointer signal; and
information generating means for generating error information indicative of presence or absence of the error corresponding to the data signal in accordance with the error pointer signal demultiplexed by the demultiplexing means.
The above-mentioned reception apparatus preferably further comprises converting means for converting the data signal outputted from the demultiplexing means and including the video signal composed of the first number of words and generated for each block, into a data signal including the video signal composed of a predetermined second number of words and generated for each block, and outputting the converted data signal.
Further, according to the third aspect of the present invention, there is provided a transmission method including the following steps of:
generating error location information which an error occurs in each block, in accordance with a data signal including a video signal composed of a predetermined first number of words and generated for each block, and an error information signal indicating presence or absence of the error corresponding to the data signal; and
multiplexing the generated error location information and the data signal into a multiplexed signal, and transmitting the multiplexed signal through a transmission line.
The above-mentioned transmission method preferably further includes a step of converting a data signal including a video signal composed of a predetermined second number of words and generated for each block, into a data signal including a video signal composed of the first number of words and generated for each block.
Still further, according to the fourth aspect of the present invention, there is provided a reception method including the following steps of:
receiving a transmission data signal including a data signal and an error pointer signal through a transmission line, the data signal including a video signal composed of a predetermined first number of words and generated for each block, the error pointer signal indicating error location information at which an error occurs corresponding to the data signal;
demultiplexing the received transmission data signal into the data signal and the error pointer signal, and outputting the data signal and the error pointer signal; and
generating error information indicative of presence or absence of the error corresponding to the data signal, in accordance with the demultiplexed error pointer signal.
The above-mentioned reception method preferably further comprises a step of converting a data signal including a video signal composed of the first number of words and generated for each block, into a data signal including a video signal composed of a predetermined second number of words and generated for each block, and outputting the converted data signal.
In the above-mentioned aspects of the present invention, the error location information indicates information of a head location of the error in the block of the data signal or the video signal. Also, the transmission line is preferably a digital data transmission line in conformity with a standard for SDTI (Serial Data Transport Interface) specified by SMPTE (Society of Motion Picture and Television Engineers) 305M.